The present invention relates to improvements in methods of and in apparatus for gathering piles or stacks of sheets, panels, laminae and analogous flat objects preparatory to pivotally connecting the stacked objects to each other by the convolutions of coil springs or analogous coupling or connecting devices.
It is known to assemble sheets of lined or otherwise imprinted paper or the like into stacks, to provide the sheets with rows of perforations which are adjacent to one longitudinal or transverse marginal portion of the stack, and to use a length of a coil spring which pivotably connects the sheets of the stack to each other. The convolutions of the coil spring extend through groups of aligned holes in the stack and the ends of the inserted coil spring are often deformed and/or otherwise treated to ensure that the coil spring cannot be accidentally separated from the stack.
It is also known to shift the sheets of an assembled stack relative to each other prior to introduction of the coil spring. The purpose of such shifting is to impart to each through hole of the stack a shape which is more likely to permit unimpeded and predictable introduction of convolutions of the coil spring. This can be accomplished by imparting to each hole a shape (e.g., a V-shaped outline) having a configuration more closely approximating that of the convolutions than a straight hole. The presently known means for changing the configurations of holes in the stacks of sheets prior to the introduction of the coil spring include at least one pin- or stud-shaped sheet shifting element, normally at least one row of such elements, which is or which are introduced into the originally straight hole or holes and is or are thereupon pivoted to thus shift at least some sheets of the stack relative to the other sheet or sheets. The thus manipulated stack is ready to be assembled with a coil; this involves the introduction of successive convolutions of the coil at one end of the spine of the stack and rotation of the coil so that its convolutions advance toward the other end of the spine. Deformation of holes in the spine of the stack prior to assembly with the coil is intended to facilitate the threading of convolutions into the spine even if the diameters of perforations in the individual sheets, panels or layers of the stack only slightly exceed the diameter of the wire or other material of which the coil is made.
Apparatus of the just outlined character can be utilized in semiautomatic or fully automated production lines for the making of legal pads, other pads, calendars, brochures or analogous commodities. In many instances, the production line further comprises means for assembling a succession of stacks by subdividing webs, strips or large panels of paper, foil, cardboard or the like into sheets of desired size and/or shape. Such subdivision can take place simultaneously with the making of rows of perforations and/or with the application of printed matter to selected sheets or to each sheet of the stack. The thus treated sheets are gathered into piles or stacks each of which contains a predetermined number of sheets, and the perforations of the thus gathered sheets of the stack overlie each other to jointly form a row of elongated holes extending all the way from one to the other outermost sheet of the stack. This is a prerequisite for the introduction of the convolutions of a coil spring which, when properly inserted, permits pivoting of one or more sheets of the thus obtained commodity relative to the other sheet or sheets.
German patents Nos. 2 653 759 A1 and 2 804 180 A1 disclose methods of and apparatus for assembling the sheets into stacks of overlapping sheets in such a way that the holes consisting of perforations extending along registering marginal portions of the sheets are ready to receive the convolutions of a coil spring. The patented apparatus comprise two confronting rows of studs or pins which face each other and means for moving the two rows of such component parts relative to (toward and away from) each other. Insertion of the two rows of studs or pins into the holes of a stack of sheets is followed by a pivoting of the studs or pins with the result that each originally straight hole of the stack is converted into a substantially V-shaped passage for the convolutions of the coil. Such conversion of the originally straight holes is followed by extraction of the pins or studs from the stack and the threading of successive arcuate convolutions of the coil into successive V-shaped passages.